Engine starter



J. F. KOEPFLE ENGINE STARTER Filed Jan. 2, 1941 June 15, 1943.

2 Sheets-Sheet l INVENTORI (Ilse oh 1 Koe afe June 15, 1943. J KOEPFLE 2,321,686

ENGINE STARTER Filed Jan. 2, 1941 2 Sheets-Sheet 2 .Patented June 15, 1943 ENGINE STARTER Joseph F. Koepfle, Detroit, Mich, assignor of one-half to Leo G. Koepfle, Silver Spring, Md.

Application January 2, 1941, Serial No. 372,928

8 Claims.

My invention of which the following is a detailed description relates to engine starting drives wherein force is transmitted from a rapidly rotating pinion to the gear on a fly-wheel. In starting or setting in operation internal combustion engines or the like it is customary to turn over the fly-wheel and crank shaft by means of force applied from an electric motor or the like. Devices for engaging the pinion with the gear on the fly-wheel and applying force to the latter are well known and in extensive use. In the majority of instances the operative connection for the pinion includes a torsional spring or driving connection. It is an object of my invention to eliminate the use of a spring as a connecting element in the rotation of the driving pinion.

It is also an object of my invention to prevent the pinion from being forced into a binding engagement with the gear wheel due to limitation in motion of the pinion arising from the use of an abutment n the driving shaft or sleeve. Among the objects of my invention is to relieve strains occurring in the abnormal operation of the starter when the fly-wheel fails to move due to the motor being bound by friction or the like.

My invention likewise protects the starting mechanism against mechanical failure or breakage. In the practice of my invention the starting pinion is held up to engagement with the flywheel gear with increasing force so that the mechanism is protected against shock but the maximum torque may be applied.

It is a further object of my invention to apply positive driving force to the pinion from both sides of the threaded sleeve by which it is rotated.

Other objects and advantages of my invention will be apparent from the following detailed description of the preferred form as illustrated in the accompanying drawings in which Fig. l is a longitudinal vertical section of the improved starting motor drive;

Fig. 2 is a side elevation of the same;

Fig. 3 is a longitudinal vertical section of a slightly modified form;

Fig. 4 is a perspective view of the collar shown in Fig. 3 and Fig. 5 is a longitudinal vertical section of further modification of the invention.

The essential features of my improved device are that the customary starting pinion shall be operated from a screw threaded sleeve which in turn is connected at opposite ends to the drive shaft. In this way the threaded sleeve receives the driving force evenly and transmits it to the pinion without creating any whip or torsional strain. It is characteristic of my invention also that the pinion is held up to engagement with the gear by a compression spring and that on the occasion of abnormal load on the pinion, the stress is transmitted through the sleeve to the compression spring. When the pinion encounters abnormal resistance the threaded sleeve compresses the spring and retracts longitudinally along the drive shaft. This in turn increases the driving force transmitted through the pinion. However, if the load becomes excessive the pinion may be caused to retract with the sleeve and thus protect the mechanism against mechanical failure or breakage.

As illustrated in Fig. 1, I have shown the case I of an electric starting motor having a rotary drive shaft 2. Suitably positioned on this drive shaft is a thrust block 3 fixed to the shaft by means of a set screw 4. The outer face of the thrust block 3 has a series of roller bearings 5 by which the position of the pinion is limited. The outer surface of the thrust block also has a half collar 6 which overlies the shaft and forms a driving engagement for the device.

A sleeve 1 is provided to be carried on the shaft 2 and subject to slidable movement thereon. This sleeve has an external screw thread 8 which begins at the inner end of the sleeve and extends for the greater part of its distance. At the inner end the sleeve 1 is cut away as shown in Fig. 2 to provide a semi-cylindrical recess complementary to the extension 6 on the thrust block 3. It will be observed that the outer surface of the extension 6 coincides with the surface of the sleeve 7 and lies below the threads 8.

A pinion 9 is provided with internal screw threads as shown in Fig. 1 conforming to the threads 8 on the sleeve. This pinion 9 traverses the sleeve 7 longitudinally and the teeth of the pinion engage the teeth of the fly-wheel gear ii].

The outer end I! of the sleeve 1 is enlarged. It is also cut away as shown in Figs. 1 and 2 to provide an opening I2. On the shaft 2 opposite the opening l2 there is a set screw i3 holding a drive member l4. This member M as shown in the drawings extends for a less distance longitudinally of the shaft than the opening i2 so that the sleeve 1 is permitted a limited longitudinal movement.

The sleeve 1 is held inward by means of a compression spring l5 resting on the enlarged end H of the sleeve, The opposite end of the spring rests against an adjustable tensioning collar It. The collar l6 in turn is adjusted by means of set screws I'l passing through a stop collar l8 fixed to the shaft 2 by means of set screws l9 or the like.

The arrangement above described provides the minimum of parts for a direct drive from the motor shaft 2 to the pinion 9 but force is applied at opposite ends of the sleeve 1. In the customary manner, the pinion 9 is therefore urged into engagement and driving relationship with the gear I 9. In this operation the compression spring l holds the sleeve 1 in its position with the recessed end against the thrust block 3. On the occurrence of an abnormal load, the sleeve 1 will continue to rotate with the shaft 2 by reason of its engagement with the half collar 6 and the drive member I4. However, the force will be applied in compressing the spring I 5 and retracting sleeve 1. This in turn transmits the combined driving force from the shaft 2 and spring It to the pinion 9. However, if the resistance is excessive the pinion 9 will also be retracted by the sleeve 1 and thus the mechanism protected from breakage.

A slightly different form of the invention is shown in Fig. 3 where the enlarged end 23 of the sleeve 7 is indirectly connected to the shaft 2.

This connecting means comprises a drive member 2| of irregular cross-section. A typical crosssection hexagonal in form is shown in Fig. 4 and it is to be understood that the enlarged end 28 of the sleeve is of the same hexagonal form and slidable within the drive member 2|. The drive member is carried on the collar 22 which in turn is fixed to the end of shaft 2 by means of set screw 23.

The front end of the drive member 2| has an inwardly directed flange 24 loosely surrounding the screw threaded end of sleeve 1. The force of compression spring [5 is in part opposed by a smaller coil spring 25 with its ends resting upon the terminal flange 24 and the front face of the enlarged end 26. The operation of thisarrangement is similar to that above described for the arrangement in Figs. 1 and 2. The added feature is the differential action between the compression springs 15 and 25 which serves to accelerate the action of the pinion 9 both in normal and abnormal operation.

In Fig. 5, I have shown a still further modification in which the pinion 9 has a small collar 26 to which a shell 21 is fastened. Thisshell at its open end carries a nut 28 which is screw threaded upon sleeve 1. In this instance the thrust member comprises a small collar 29 attached to the drive shaft 2. One end of the collar 29 has a flange 30 against which a thrust bearing 3! rests. This thrust bearing is of usual anti-friction arrangement. The set screw 31 indicates how torque is applied. Shell 27 and nut 28 work together on momentum and collar 29 is the driver, and the pitch of the threads of sleeve I creates the momentum for shell 21 and nut 28 forward to thrust bearing 3|. When the nut 28 reaches the thrust bearing 3| then the sleeve 1 is pushed back towards spring l5 which is compressed, thereby creating torque pressure on the threads of sleeve 1 thereby forcing shell 21 and nut 28 back to position as shown in the drawings.

The sleeve 29 is irregular in its extent as shown in Fig. 5 and similar to what is shown in Fig. 2 at 6. The inner end of sleeve 1 conforms to the shape of sleeve 29. In this manner sleeve 1 may slide longitudinally of shaft 2.

Compression spring l5 rests against the outer end of sleeve 1 and against an abutment 32 which is suitably fastened to shaft 2.

This form of the invention also provides for traversing the pinion 9 along the shaft 2 being driven forward by the nut 28 on the screw threaded sleeve 1. This traverse is limited by engagement with the thrust bearing 3|. On the occurrence of abnormal or excessive load further force from the shaft 2 will retract sleeve 1 against the compression spring I5.

It might be noted further that, whereas the embodiments shown in Figures 1 to 4 are of the inboard type of drive with the starting motor placed in front of the large spring, that of Figure 5 is of the outboard style wherein the starting motor is placed in back of the large spring. In other words, the drive may be from either end of the shaft.

The pressure-responsive drive for the pinion with the differential spring action serves to force the pinion forward immediately when the starting motor operates and to repeat the forward movement whenever the pinion meets momentary resistance. Thus the meshing of pinion with the fly-wheel gear is repeated until the two are in final driving engagement or the resistance is so reat as to unclutch the sleeve from the half-collar clutch. In the case illustrated in Fig. 3, sleeve 1 is rotated by both 2| and 6 but increase of load may momentarily disengage I from 6 until the larger spring restores the driving engagement with the pinion advanced.

I have illustrated several forms in which my invention may be embodied without however limiting other than by the scope of the appended claims.

What I claim is:

1. An engine starter drive comprising a drive shaft, a threaded sleeve longitudinally slidable on said shaft, a thrust block fixed on the shaft, means on the block and on one end of the sleeve for sliding interengagement, a drive member fixed on the shaft, means for providing relative sliding engagement between the second end of the sleeve and said drive member, resilient means resisting the sliding movement of the sleeve away from said blodk, and a pinion carried on said sleeve.

2. An engine starter drive comprising a drive shaft, a sleeve longitudinally slidable on said shaft, said sleeve having a recess at one end and an extended screw thread extending back from said recess, drive means operatively connecting the opposite end of the sleeve with the shaft for rotation therewith and for sliding movement longitudinally thereon, a thrust block fixed on the shaft, means on the block for sliding engagement with the threaded end of the sleeve, resilient means resisting the sliding movement of the sleeve away from the thrust block, and a pinion carried on said sleeve.

3. An engine starter drive comprising a drive shaft, a sleeve slidable on said shaft, said sleeve being cut away at one end to provide a recess having longitudinal side walls, a screw thread extending over the recessed part and inwardly from the end of the sleeve, an enlarged opposite end on the sleeve, a drive member operatively connected to the shaft, means on said member for longitudinally sliding engagement with the sleeve, a coil spring on the shaft having one end against the enlarged end of the sleeve and the other end anchored relatively to the shaft, a thrust block fixed on the shaft beyond the recessed end of the sleeve, an extension on the block fitting with in the recessed part of the sleeve, and a pinion slidably carried on the threaded portion of the sleeve and over the extension on the thrust block.

4. An engine starter drive comprising a drive shaft, a sleeve slidable on said shaft, said sleeve being cut away at one end to provide a recess having longitudinal side walls, a screw thread extending over the recessed part and inwardly from the end of the sleeve, an enlarged opposite end on the sleeve, a drive member operatively connected to the shaft, means on said member for longitudinally sliding engagement with the sleeve, a coil spring on the shaft having one end against the enlarged end of the sleeve, means on the shaft to anchor the opposite end of the spring, a thrust block fixed on the shaft beyond the recessed end of the sleeve, an extension on the block fitting within the recessed part of the sleeve, and a pinion slidably carried on the threaded portion of the sleeve and over the extension on the thrust block.

5. An engine starter drive comprising a drive shaft, a sleeve slidable on said shaft, said sleeve being cut away at one end to provide a recess having longitudinal side walls, a screw thread extending over the recessed part and inwardly from the end of the sleeve, an enlarged opposite end on the sleeve, an opening in the side of said enlarged end, a drive member operatively connected on the shaft in said opening and of less length than the opening, a coil spring on the shaft having one end against the enlarged end of the sleeve and the other end anchored relatively to the shaft, a thrust block fixed on the shaft beyond the recessed end of the sleeve, an extension on the block fitting within the recessed part of the sleeve, and a pinion slidably carried on the threaded portion of the sleeve and over the extension on the thrust block.

6. An engine starter drive comprising a drive shaft, a sleeve slidable on said shaft, said sleeve being cut away at one end to provide a recess having longitudinal side walls, a screw thread extending over the recessed part and inwardly from the end of the sleeve, an enlarged opposite end on the sleeve, a drive member operatively connected on the shaft beyond the enlarged end of the sleeve, a coil spring around the shaft between said end of the sleeve and the drive member, a drive cohar on the drive member extending over the enlarged end of the sleeve and engaging the latter for rotation with the shaft, a thrust block fixed on the shaft beyond the recessed end of the sleeve, an extension on the block fitting within the recessed part of the sleeve, and a pinion slidably carried on the threaded portion of the sleeve and over the extension on the thrust block.

7. An engine starter drive comprising a drive shaft, a sleeve slidable on said shaft, said sleeve being cut away at one end to provide a recess having longitudinal side walls, a screw thread extending over the recessed part and inwardly from the end of the sleeve, an enlarged opposite end on the sleeve of irregular cross-section, a drive member fixed on the shaft beyond the enlarged end of the sleeve, a coil spring around the shaft between said end of the sleeve and the drive member, a drive collar on the drive member extending over the enlarged end of the sleeve, said drive collar having an inwardly directed terminal flange and an internal crosssection conforming to the irregular cross-section of the sleeve, a second coil spring between the end of the sleeve and said flange, a thrust block fixed on the shaft beyond the recessed end of the sleeve, an extension on the block fitting within the recessed part of the sleeve, and a pinion slidably carried on the threaded portion of the sleeve and over the extension on the thrust block.

8. An engine starter drive comprising a drive shaft, a threaded sleeve longitudinally slidable on said shaft, a thrust block fixed on the shaft, a thrust bearing on the block, means on the block and on one end of the sleeve for sliding interengagement, a stop on the shaft, a coil spring on the shaft between the stop and the sleeve, a pinion, and means connecting the pinion with the sleeve to cause the latter to move relatively to the thrust block.

JOSEPH F. KOEPFLE. 

